Patent GB-619359-A (GB)
Title: An improved auxiliary device on sewing-machines for zigzag sewing
IPC: D05B21/00
Filed: 1946-12-04
Abstract: 619,359. Sewing-machines. OSWALD, A. Dec 4, 1946, No. 35914. Convention date, Dec. 15, 1945. [Class 112] Zig-zag stitching attachments.-A zig-zag stitching attachment, in which the mechanism occupies a small space and is arranged to one side of the seam to improve visibility, comprises a presser-foot and a deflector both oscillatable about an axis parallel to the seam, a vertically adjustable member carrying two cam levers which engage opposite sides of the presserfoot shank, and a cam member actuated by the needlebar to engage the two levers alternately to produce the required lateral movements of the presser-foot. The width of the zig-zag is adjustable, and the lateral movement of the presser-foot may be suspended without affecting the adjustment. In the arrangement shown, the presser-bar 1 has clamped to it a guide 3 which carries the following parts : on a pivot 22, a deflector 25 ; on a pivot 6, the presser-foot 5, which has a clearance aperture round the pin 22 ; in vertical guides, a slide 7 having cam levers 30, 32 pivoted to it at 31, 33 respectively ; and, in a circular aperture in a depending lug 9, a disc having a crank pin 15, engaging a horizontal channel in the slide 7, and a head 14 by which it can be rotated to shift the slide 7 vertically. The head 14 is held in set position by the engagement with teeth thereon of a leaf spring 19 carried on the rear end of the pivot pin 22 of the deflector 25, this spring pressing the deflector and presser-foot together and against the guide 3 to produce a certain amount of friction for control of the movements of these members. Clamped on the needle-bar 37 is a member 38, on which is pivoted near its upper end an arm 41 carrying at its lower end a cam pin 36 arranged to engage the deflector 25 and cam levers 30, 32 ; the arm 41 is engaged by a leaf spring 44 and is shaped so that the spring tends to return it to its mid-position from either side. In the position shown in Fig. 8, the plate 41 is in its right-hand position and is ascending, the cam-pin 36 shifting the presser-foot to the left by means of the lever 30. On further ascent, the pin 36 rocks the deflector 25 anti-clockwise, and at the end of the subsequent descent of the needle-bar the plate 41 will move to its mid-position under the action of its spring so that on the next ascent the cam-pin will move along the left-hand side of the deflector and actuate the cam-lever 32 to shift the presser-foot to the right. By vertical adjustment of the slide 7 carrying the cam-levers the latter are positioned to co-operate with a wider or narrower part of the shank of the presser-foot to vary the lost motion and thus the amplitude of movement of the presser-foot : in the lowest position of the slide the presser-foot is held between the lever 32 and a fixed abutment 54 to produce a straight seam in line with the centre of the zig-zag seam. A straight seam in line with the right-hand edge of the zig-zag seam may be produced by locking the arm 41 in its right-hand position by means of a detent 45 held in either position by a wire spring which at its other end provides a thread-guiding eye. Presser-feet.-The under surface of the presser-foot 5 is curved transversely, as shown in Fig. 8, correspondingly to its arc of oscillation, and is formed with longitudinal teeth for better engagement with the fabric. The shank of the presser-foot is curved laterally so that the mechanism lies to one side of the seam and does not obscure the view of the work.